This section provides background information related to the present disclosure which is not necessarily prior art.
In a conventional vehicle, kinetic energy is converted into heat through friction braking. For example, when a driver applies a mechanical force to a brake pedal, a master cylinder converts the mechanical force into hydraulic pressure. The hydraulic pressure applies a force to a friction material, such as a brake pad, and forces the friction material against the sides of a disc attached to a wheel. The friction material against the disc creates friction and causes the wheel to slow or stop. Modern vehicles utilize a brake booster to reduce the amount of mechanical force the driver is required to apply to the brake pedal to effectively slow or stop the vehicle. The brake booster uses vacuum from the engine intake to boost the force applied by the brake pedal on the master cylinder.
Electrical vehicles rely solely on an electric propulsion system. Hybrid electric vehicles combine an internal combustion engine with an electric propulsion system. Electric and hybrid electric vehicles do not produce a sufficient source of vacuum pressure for conventional brake booster actuation. Internal combustion, diesel, stratified charge, and spark ignition direct injection engines have higher efficiency and produce less vacuum than typical internal combustion engines. As such, alternative arrangements are employed in these vehicles to boost the force applied to the brake pedal on the master cylinder. For example, electric, hybrid electric, and fuel efficient internal combustion engine vehicles may include electro-mechanical brake boosters.
Hybrid and electric vehicles are generally known to employ regenerative braking to activate a motor, such as a generator, during deceleration of the vehicle. Energy conventionally dissipated as heat during frictional braking can be converted into electrical energy and stored in a battery. In this manner, energy may be conserved for subsequent use thereby extending the electrical range of the vehicle under electrical power. Friction braking may also be blended with regenerative braking by a vehicle ECU to provide the brake force requested by the driver.
While known braking systems have proven to be successful for their intended purposes, a continuous need for improvement in the relevant art remains.